Optical surface defect inspection apparatus and optical surface defect inspection method

Abstract

The invention provides an optical surface defect inspection apparatus and an optical surface defect inspection method that reduces an influence from a dead zone of a sensor array and that reduces the influence from reduction of a detected light amount in a case of extending over light receiving elements, thereby enabling a defect inspection with high sensitivity. According to the invention, a subject is irradiated with an inspection light, an image is formed on the sensor array including the light receiving elements separated by the dead zone insensitive to light scattered by a surface of the subject and arranged in a plurality of lines, outputs from two adjacent light receiving elements are added, and a defect on the surface of the subject is inspected for based on the result of the addition.

What is claimed is: 
     
         1 . An optical surface defect inspection apparatus including:
 an irradiation means irradiating a subject with an inspection light;   a sensor array including light receiving elements separated by dead zones insensitive to light scattered by a surface of the subject and arranged in a line;   a scattering optical means light focusing the scattered light onto the sensor array;   a plurality of addition means adding outputs from two adjacent the light receiving elements; and   a processing unit inspecting for a defect on the surface of the subject based on outputs from the addition means.   
     
     
         2 . The optical surface defect inspection apparatus according to  claim 1 , wherein
 the sensor array has the dead zone arranged at an oblique angle with respect to a direction perpendicular to the line.   
     
     
         3 . The optical surface defect inspection apparatus according to  claim 2 , wherein
 the oblique angle is in a range of 25 to 45 degrees.   
     
     
         4 . The optical surface defect inspection apparatus according to  claim 1 , including:
 a first addition means as one of the plurality of the addition means;   an average value calculation means calculating an average of outputs from two second addition means adjacent to the first addition means;   an output difference calculation means obtaining an output difference between the first addition means and the average value calculation means; and   the processing unit inspecting the defect on the surface of the subject based on the output from the output difference calculation means.   
     
     
         5 . The optical surface defect inspection apparatus according to  claim 1 , wherein
 the subject is a magnetic disc or an IC wafer in a form of a disc, and the apparatus further includes a scanning means two-dimensionally scanning the inspection light on the surface of the subject the inspection light.   
     
     
         6 . An optical surface defect inspection method including:
 an irradiation step of irradiating a subject with an inspection light;   a step of forming an image on a sensor array including light receiving elements separated by dead zones insensitive to light scattered by a surface of the subject, the receiving elements being arranged in a line;   a plurality of addition steps of adding outputs from two adjacent light receiving elements; and   a processing step of inspecting for a defect on the surface of the subject based on the result of the addition step.   
     
     
         7 . The optical surface defect inspection method according to  claim 6 , wherein
 the sensor array has the dead zone arranged at an oblique angle with respect to a direction perpendicular to the line.   
     
     
         8 . The optical surface defect inspection method according to  claim 6 , including:
 an average value calculation step of calculating an average of outputs of two second addition steps adjacent to a first addition step as one of the plurality of the addition steps;   an output difference calculation step of obtaining an output difference between the first addition step and the average value calculation step; and   the processing step of inspecting for the defect on the surface of the subject based on the output of the output difference calculation step.